The goal of this research is to isolate proteins characteristic of the surface of transformed cells. Purification of such unique proteins and administration to an individual animal might activate an immune response enabling tumor rejection. Our proposed procedure for the isolation of cell surface protein involves synthesis of macromolecular reagents consisting of a) a reactive group capable of forming a specific covalent bond with proteins; b) a macromolecular carrier, and c) a linkage between the two that is stable under normal physiological conditions, but may be selectively broken. The reactive group can be designed with many variations in specificity, i.e., directed at thiol groups, amino groups, or more specifically, at the active sites of enzymes such as proteases, or at cell surface receptor sites. The carrier can either be soluble (e.q., ferritin) or insoluble (e.g., agarose). The advantages of the methods using the solid phase reagents include high yield of selected protein, ability to wash away solubilizing agents, minimal contact with degradative enzymes, minimal manipulation, and the possibility of regenerating native protein. Purified proteins characteristic of transformed Balb/c 3T3 cells will be tested in Balb/c mice for the ability to enhance tumor rejection.